This invention relates to new dyes and dye precursors which are particularly suitable for coloring keratin fibers, to the use of these dyes and dye precursors and to colorants containing these dyes and/or dye precursors.
Among the various products available for the cosmetic treatment of the human body, formulations for modifying or shading the color of the hair occupy a prominent position. Disregarding blonding preparations which lighten the hair oxidatively by degrading the natural hair dyes, three types of colorants have long been of importance in the coloring of hair:
So-called oxidation colorants are used for permanent, intensive colors with corresponding fastness properties. Oxidation colorants normally contain oxidation dye precursors, so-called primary intermediates and secondary intermediates. The primary intermediates form the actual dyes with one another or by coupling with one or more secondary intermediates under the influence of oxidizing agents or atmospheric oxygen.
Colorants or tints containing substantive dyes as their coloring component are normally used for temporary colors. Substantive dyes are based on dye molecules which are directly absorbed onto the hair and do not require an oxidative process for developing the color. Dyes such as these include, for example, henna which has been used since ancient times for coloring the body and hair.
In recent years, a new coloring process has received considerable attention. In this process, precursors of the natural hair dye, melanin, more particularly derivatives of indole or indoline, are applied to the hair and then form xe2x80x9cnature-likexe2x80x9d dyes in the hair in the course of oxidative processes. One such process using 5,6-dihydroxyindolines as the dye precursors is described in EP-B1 530 229. If preparations containing 5,6-dihydroxyindoline are applied, in particular repeatedly, people with gray hair can be given back their natural hair color. Color development can be carried out with atmospheric oxygen as sole oxidizing agent so that no other oxidizing agent has to be used.
Although it is possible in principle to formulate colorants containing only a dye or a dye precursor, such colorants are of only limited significance in practice with the exception of a few products which contain melanin precursors for example.
Instead, commercial hair coloring products normally contain a mixture of about 3 to 8 different dyes and/or dye precursors. However, the individual dyes generally differ in their capacity to be absorbed onto the hair and in their fastness to light, perspiration, rubbing and washing which, in addition, can be determined to a considerable extent by the structural properties and condition of the hair. These differences are pronounced above all when substantive dyes are used for adjusting the shade in oxidation hair colorants, as has hitherto been essential for many shades.
Accordingly, there is often a need in the development of new hair colorants to carry out extensive tests not only to obtain certain shades, but above all to ensure that the color is stable for the required period both in regard to shade and in regard to intensity.
It has now surprisingly been found that many of the problems mentioned above can be completely or at least partly avoided by the use of substances which possess both the properties of a substantive dye and the properties of an oxidation dye precursor, a melanin precursor or another substantive dye. In particular, it has been found that the dyes have a very high capacity for absorption onto the hair comparable with that of known hair dyes or hair dye precursors and lead to brilliant intensive hair colors. By virtue of the molecular linkage, the problem of differing fastness properties of the two dyes or dye precursors can thus largely be overcome in many cases.
Substances such as these, which are referred to hereinafter as xe2x80x9chybrid dyesxe2x80x9d, are new.
In a first embodiment, there fore, the present invention relates to hybrid dyes, more particularly for coloring keratin fibers, which correspond to formula (I):
Xxe2x80x94Sxe2x80x94Yxe2x80x83xe2x80x83(I)
where
X is a group derived from a substantive dye,
Y is a group derived from
an oxidation dye precursor of the secondary or primary intermediate type,
a derivative of indole or indoline as a precursor of melanin or
a substantive dye and
S is a direct bond or a spacer group, with the proviso that S is not an alkylene, mono- or polyhydroxyalkylene group where Y is derived from a substantive dye.